Questions on this guy's techniques

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#1

I don’t know if some of you have seen this site or not, but it’s rather impressive! :eek: http://www.mmrca.org/lance/sledframe.html

I had a couple of questions on his techniques though. If you check out 12/2/2003, you’ll see how he’s making his molds. Rather than use gelcoat, he’s using Duratec in it’s place. What are the pros and cons of this? One pro I can see right away is that you don’t have to worry about it “alligatoring” on you. I’m not sure if he’s letting it dry completely or just tacking up, but I would guess dry completely. Otherwise wouldn’t you get print through if you tried to lay-up before then? If you do let it dry, that seems like it would be a lot easier than waiting around for your gelcoat to hit just the right stage. Then your also ready to sand any imperfections right out of the mold. There’s got to be some negatives here, help me out. :rolleyes:

On 11/30/2004, you can see him make his first parts. This time it says “Dupont automotive primer,” not Duratec, and it’s a lighter gray. If that’s the case, does it work well? Would Duratec be better? Gelcoat even better than that? Also, how would he connect the rudder base halves? After trimming them flush to the mold, he’ll just bolt it back together and lay a strip inside and press on it as well as he can?

#2

Ill be interested in the answer to these questions as well.
Thanks For the link, very interesting, buliding an SR-71 in your garage, What a project !

#3

Not just building a SR-71, but a 12 or 13’ SR-71! He said he has about a grand in the top half of the mold alone! :eek:

#4

It made of carbon then?

#5

No, epoxy and glass. He says that layers and layers, and gallons and gallons of resin start to add up. Very sweet though. If you look, he’s got three years invested in the project.

edited for typo

#6

I am anxious to read it myself.

I could see a thousand in the mold.

Im burning thru materials faster than Id like…

#7

Thank you the great link!

Most Duratec resin that I have worked with is a Gel coat.

It is easy to spend alot of $'s if buy a gallon at a time but a 55 gallon drum of GP lamination resin is easy $800 (last time I bought one was around $700 but with Bush’s buddies running up the price of crude oil…).

#8

You guys want me to try Duratec as a gel coat and see how it goes? lol

But seriously, Duratec primer is good stuff. Cures very hard, I’ve already hit it with a hammer “just to see” and it held, no cracking. Course I only weigh 165 soaking wet. :stuck_out_tongue:

#9

I have resurfaced molds with duratec. Works fine

#10

Interesting. So between this guy, pf_composites, dual twill’s responses, and this PDF:
http://www.duratec1.com/Application_Guides/ag1.pdf it seems like it’s pretty safe to say Duratec can be substituted for gelcoat, especially if you plan on painting the piece afterwards.

The place I’ve been buying my gelcoat from runs about $100 a gallon :eek: and Duratec is about $60 or so…

I can spray Duratec, let it dry and not have to worry about it wrinkling on me…

Any imperfections can be sanded immediately after washing off PVA… (Yeah, I know, there shouldn’t be, but you never know :rolleyes: )

It’s ready for paint after that, you don’t have the extra step of applying primer after demolding…

I’m really having a tough time seeing why I wouldn’t want to switch to Duratec rather than gelcoat here.

Also, it hasn’t really been answered, has anyone just sprayed a regular primer in their molds and layed up on top of that like this guy seems to be doing for his parts?

Finally, if I am going to switch, is one polyester primer as good as another? For instance, I’m not sure if I can get Duratec locally, but I know I can get Evercoat’s Slick Sand. Would it be just as good? I just wonder how much Duratec’s going to cost me after shipping and if Slick Sand will work just as good…

#11

Just thought of one more thing, how long would a mold that was had a Duratec surface last? Obviously not as long as tooling gelcoat, but as long as normal gelcoat? To be honest, I don’t see needing more than 10 or 20 pulls from the molds I making at most.

#12

Which Duratec material are you typing about? :confused:

Duratec (RevChem) makes many products with the Duratec name on it!

#13

Doh, guess I could’ve been more specific, huh? :rolleyes: I was referring to Duratec Polyester Surfacing Primer.

#14

Have used something very much like that to repair a damaged mould, and it seems to be pretty durable. Dont think I would use it instead of gelcoat if making a mould from scratch, as gelcoat seems to me to be much easier to polish to a very good finish, and in the long term is probably going to last longer.

Chris

#15

I have to agree with CB that tooling resin’s are tougher, polish nicer and have the correct materials in them to take the many heat cycles of making parts.

If this mold is a simple one and not too big…then MAYBE.

But if I was going to do all the work to make a mold, I’d want to use the correct materials and be done with it the first time.

#16

I can see that, and figured that was the answer. So basically this guy is kinda crazy for risking making a mold of a plug he has that much invested in, right? Say you make the mold out of the correct materials, what about making parts using Duratec? Pretty much everything I make will be painted, is that a good move?

#17

right, when I did mine it was because I have sanded down the mold probally 5 times to resurface and started getting to the glass. So that is when I used the duratec and sanded that and that was my mold surface. I only have 5 or 6 pops off it and it is holding well